The use of telematics units in vehicles today permit a telematics service provider to supply a variety of services to users of the vehicle. These telematics units can be interfaced to other vehicle systems so that a variety of vehicle data can be accessed by the telematics unit and provided remotely to a call center via a cellular or other wireless communication system. Vehicle data can include such things as vehicle location obtained from a global positioning system (GPS) receiver or other means, vehicle operational data (odometer readings, speed, oil life, diagnostic information, etc.), vehicle identification (VIN, electronic module serial numbers, etc.) and other data, including crash sensor data that can automatically initiate an emergency call to the call center in the event that a vehicle impact is detected. Whether the result of an automatic emergency call or from a manual (e.g., voice or pushbutton) input, an emergency call to the call center can be handled by an advisor at the call center who is able to contact an emergency dispatcher at a PSAP.
Currently, in these emergency situations, one system known to the inventor provides enhanced features that include (1) the ability of the advisor at the call center to obtain various vehicle data, such as location and other information that can be used to help assess the vehicle situation and severity of the emergency, and (2) the ability to connect the call between the vehicle and call center with the call to the PSAP to provide a three-way call that permits voice communication between persons at the vehicle and PSAP. In some such instances, it can be desirable to obtain additional vehicle data during this three-way call, in which case the advisor switches the call within the call center to a data modem that communicates electronically with the telematics unit over the three-way call to obtain the desired data from the vehicle. During this time, the advisor is not able to communicate over the three-way call with persons at either the vehicle or PSAP. Furthermore, the dispatcher or other PSAP personnel is forced to wait for the data transmission to complete which involves using modem signalling that is audible to the PSAP personnel.